This invention relates to fibers having low coefficient of friction surfaces and methods for producing such fibers. The fibers may be incorporated into fabrics to produce articles of clothing that reduce the coefficient of friction between the articles of clothing and the body surface of a wearer or the external surface of an object or fluid media.
There are many well known processes for manufacturing fibers. Fibers are typically structures whose length is significantly greater than any of their other dimensions usually, their length is at least 100 times as large as their diameter. Fibers may be natural, synthetic, organic or inorganic. Often, the bulk polymers from which synthetic fibers are formed, maybe useful as plastics or films depending upon the type and degree of molecular orientation and the relative dimensions of the finished structure.
Fibers are usually produced by drawing, spinning or stretching a bulk material so that the molecules are predominantly aligned in the drawn, spun, or stretched direction. Subsequent drawing of the fiber below its melt temperature significantly alters the fiber""s mechanical properties.
Fibers may also be produced by slitting an oriented film or sheet. If prepared from oriented sheet, the slit sheet will require subsequent drawing to obtain the required fiber properties.
Most synthetic fibers may be produced as long continuous filament or as staple. Staple is produced by cutting continuous filament into short lengths. Most natural fibers are produced as staple, with silk being a notable exception.
Continuous filament and staple are often post treated to alter their surface characteristics. Such surface treatments may include scouring by surface active agents to remove surface impurities, sizing by a surface coating to protect the fiber during weaving, dyeing to modify the color of the fiber and lubrication by refined petroleum products to reduce static and the coefficient of friction.
It is apparent in the prior art that coating a staple or filament will usually provide a fiber having a surface completely covered by the coating. In cases where a low coefficient of friction is desired, this may sometimes be undesirable. For applications in which a low coefficient of friction might be needed on the top and/or bottom surface of a fiber, uniformly coated fibers might not provide the optimum balance of properties after being woven into a fabric which is used to create clothing apparel.
Most apparel is made out of many materials, natural and man-made. They include cotton, wool, silk, linen, leather, vinyl, nylonxe2x80x94polyamides and polyamide co-polymers, LYCRA SPANDEX(trademark) in different filament configurations, orlon polyvinylidene fluoride, such as KYNAR(trademark) and polyester, for example, polyethylene terepthalate, glycol modified polyesters, such as PETG, KODURA(trademark), rayon, orlon cellulosic fiber blends, and the like, as well as blends of the above.
Of course, apparel, either directly or indirectly, contacts the body surface of the wearer. The movement of the wearer causes frictional contact between the wearer""s body surface and the apparel. This frictional contact can cause irritation, blisters, and callouses and s particularly a problem in sporting apparel wherein the formation of irritations, blisters, and callouses is exacerbated by the rapid and/or repetitious body movements related to the particular activity. Additionally, it is noted that most apparel has specific areas of high body surface/apparel contact which produces a majority of the irritations, blisters, and callouses.
One way to overcome the problems caused by frictional contact between an article of clothing and the wearer is to make the clothing from low friction fabric. Such fabric may be made from fibers that have a low friction outer surface. However, when the low friction fibers are woven together to produce a fabric the low fiber-to-fiber coefficient of friction is likely to decrease fabric stability by enabling the fibers to easily slide among themselves. This problem is recognized in U.S. Pat. No. 5,035,111 to Hogenboom et al. Hogenboom attempts to overcome the problem by spinning yarns or fibers having a low coefficient of friction with yarns or fibers having a high coefficient of friction. However, Hogenboom does not disclose modifying the fibers themselves. Moreover, Hogenboom""s fibers are not made through coextrusion, lamination, and/or coating of a film, sheet or fiber, whereby only a portion of the fiber surface exhibits a low coefficient of friction.
It has been recognized that the prior art has failed to provide a means for producing a fiber having at least one surface with low coefficient of friction characteristics yet retaining the properties desirable for weaving the fiber into a fabric (e.g., structural stability and high tensile strength).
Accordingly, it is an object of the present invention to provide a method of producing fibers having low coefficient of friction surfaces or smooth surfaces for incorporating into fabrics while retaining the properties desirable for weaving the fiber into a fabric.
Specifically, it is an object of the present invention to provide a fiber having low coefficient of friction surfaces that retains the fabric stability after being woven into a fabric.
More specifically, it is an object of the present invention to produce through coextrusion, lamination, and/or coating a fiber having at least one low coefficient of friction surface.
It is still another object of the present invention to provide a durable high tensile-strength fiber having at least one low coefficient of friction surface and being suitable for use in weaving a fabric having at least one low coefficient of friction surface.
An aspect of this invention is to provide fibers prepared from oriented film or sheet. The film/sheet is formed through coextrusion, lamination, and/or coating such that the top and/or bottom surfaces have a different coefficient of friction than the center or internal layer(s) of material. Such fibers may be twisted in preferred sequences and/or orientations such that the center layer(s), having a higher coefficient of friction, interact with other members of the fabric construction to provide increased woven fabric construction stability. This stability is realized by having the higher coefficient of friction surfaces of the coextruded, laminated, and/or coated fiber contact additional surfaces of the gross fabric structure.
Another aspect of this invention is to partially coat a xe2x80x9cbase fiberxe2x80x9d with a low coefficient of friction material such that the coated surface of the base fiber has a lower coefficient of friction than the non-coated surface. Like the fibers prepared from film or sheet, the partially coated fibers may be twisted in preferred sequences and/or orientations such that the non-coated surfaces, having a higher coefficient of friction than the coated surfaces, interact with other members of the fabric construction to provide increased woven fabric construction stability.
Still another aspect of this invention is to provide coextruded, laminated, and/or coated fibers in which the core layer/base fiber has shock absorbing characteristics (e.g., core layer(s) are open or closed celled foams). Such fibers provide increased cushioning values in addition to a low coefficient of friction on their treated surfaces.
Yet another aspect of this invention is to provide fibers in which the core layer/base fiber provides desirable thermal characteristics. For example, the core layer/base fiber may include an insulating material for restricting the escape of heat energy, or a radiant material for facilitating the escape of heat energy.
It is apparent that the fibers of the present invention may be used to create fabrics having enhanced woven fabric stability, shock absorption capacity and/or thermal properties. Thus the present invention provides for a decrease in intra- and extra- fabric coefficient of friction, while at the same time increasing fabric stability and enhancing thermal characteristics.
By using low coefficient of friction materials during either the coextrusion, lamination, and/or coating processes, a novel fiber is produced, with at least a portion of the surface of the novel fiber exhibiting low coefficient of friction, characteristics and the remaining surface portion of the fiber exhibiting relatively higher coefficient of friction characteristics.
The novel fiber can be incorporated into a fabric to produce a fabric having a smooth surface, and the smooth surface fabric can, in turn, be incorporated into clothing to produce clothing having a smooth surface.